Flame detector cooling means



March 22, 1966 F. GILBERT FLAME DETECTOR coomue MEANS 5 Sheets-Sheet 1Filed April 22, 1963 MEIL INVENTOR L.YMAN F GILBERT W ATTORNEY March 22,1966 L. F. GILBERT FLAME DETECTOR COOLING MEANS 5 Sheets-Sheet 2 FiledApril 22, 1963 MMI 1 F'IGJO INVENTOR L.YMAN F. GILBERT BY M ATTORNEYMarch 22, 1966 F. GILBERT 3,241,595

FLAME DETECTOR COOLING MEANS Filed April 22, 1963 5 Sheets-Sheet 3 FIG-6INVENTOR LYMAN F'. GILBERT BY ATTORNEY March 22, 1966 L. F. GILBERTFLAME DETECTOR COOLING MEANS 5 Sheets-Sheet 4 Filed April 22, 1963 FIG 7ATTORNEY March 22, 1966 L. F. GILBERT FLAME DETECTOR COOLING MEANS FiledApril 22, 1963 5 Sheets-Sheet 5 //Z fZ/wace INVENTOR LYMAN F'. G ILBERT' ATTORNEY United States Patent M 3,241,595 FLAME DETECTQR COOLINGMEANS v Lyman F. Gilbert, Somers, Conn, assignor to CombustionEngineering, lino, Windsor, Conn, a corporation of Delaware Filed Apr.22, 1963, Ser. No. 274,611 19 Claims. (Cl. 158-28) This inventionrelates to flame scanners or detectors and particularly to cooling meansfor the same.

An object of this invention is an improved means for cooling a flamedetector subject to being heated by the flame it is detecting.

A further object is a detector cooling system using a small amount ofair that may be supplied from the furnace normal air sources so that noadditional or special air source is necessary.

A further object is means for providing direct contact air cooling forthe detector.

Further and other objects will be apparent from the followingspecification and the attached drawings in which:

FIG. 1 is a side view partly in section of a flame detectorincorporating the present invention;

FIG. 2 is a detailed sectional view showing the detector element, itssupporting tube and the air cooling path;

FIG. 3 is an end view of the structure of FIG. 2;

FIG. 4 is a modification of the structure of FIG. 2;

FIG. 5 is a partial sectional view showing a modified air inlet;

FIG. 6 is a vertical section of burners incorporating a detector;

FIG. 7 is a liragmentary horizontal section of the burner and igniter;

FIG. 8 is a schematic showing of the air supply system;

FIG. 9 is an enlarged view of a portion of the system of FIG. 8including a schematic showing of the emergency cooling; and

FIG. 10 is a furnace end view of an oil burner nozzle with the detectorinstalled.

A flame detector in order to function must be positioned so that it canscan or see the flame or fire-ball whose presence or absence it is todetect. When so positioned the detector element which may comprise aglass envelope enclosing a space in which detector electrodes arepositioned, is subject to radiation from the flame which it is detectingand which may have a temperature of 2500 F. The heat produced by suchradiation would soon destroy the detector element unless such heat canbe rapidly dissipated. It is an object therefore of this invention torapidly dissipate such radiant heat from the detector element by passingcooling air in direct contact with and over the detector element tocarry away such radiant heat and return it to the furance with a minimumof expended energy and equipment.

Reference may be made to Armacost Patent 2,697,422 issued December 21,1954 for Boiler Furnace for a detailed showing and description of afurnace with which the detector may be used and FIGS. 6 and 10 show thedetector mechanism installed in such a furnace in position for flamescanning. The flame scanner indicated generally at 10 is shown in FIG. 1mounted in a nozzle tip 12. The scanner comprises a tubular supportingmember indicated generally at 14 and comprising a rigid support member16 secured in a suitable manner such as by welding in the nozzle tip 12to one side thereof. Secured to the rigid metallic portion 16 in anysuitable manner as by clamps 18 is a flexible metallic sleeve 20 whichin turn is connected by a suitable means such as clamps 22 to a rigidmetal pipe 24 which is secured by any suitable means such as welding 26to the shell 28 Patented Mar. 22, 1966 of the air duct supplying air tothe burner. Secured on the outer end of pipe 24, as by threads, is acasting 30 having a chamber 32 communicating with the interior of thetubular member 14 and having an air inlet 34 for directing air from asuitable source of supply to the interior of the tubular member 14. Ifdesired, an aspirator 36 having outlets 37 supplied with comparativelyhigh pressure air through the inlet 38 may be provided under certainconditions to prevent flame or hot gases from feeding back from thefurnace through the tubular member 14.

A detector element shown in more detail in FIGS. 2, 3 and 4 is enclosedwithin a tube 40 which is telescoped within the rigid element 16 andcentered by any suitable means such as ribs 42. The outboard end of thetube 40 has positioned therein a bushing 44 (FIG. 2) to which isattached a flexible conduit 46 enclosing electrical conductors 48 andterminating in a rigid section 50 which is threaded into a casting 52having a flange member 54 by means of which it may be removably securedto the outer end of the casting 30 as by bolts 56. The electricalconductors 48 are threaded through the pipe 50 and through the chamber58 in the casting 52 and lead to a terminal 60 from which suitableconnections may be made to the remainder of the detector electricalcircuit. An air inlet connection 62 is provided in the casting 52leading into the chamber 58 and the interior of the rigid member 50,flexible member 46 and the tube 40 to supply a stream of coo-ling airthrough the tube 40 and out the open end 64 thereof.

A quartz window 66 (FIG. 2) is centered in the tube 40 by pins 68 and inthe passageway through the center of the tube through which the detectorsees the flame and prevented from outward movement by pins: 70 securedin the tube 40. A wire 72 bent into generally triangular shape is fittedwithin the tube 40 and is pressed against the underside of the glass bymeans to be explained later. To hold the quartz window in position asleeve 74 of corrugated or extended surface heat transmitting orconducting material is inserted in the tube 40 and expands so as tocontact the interior surface of the tube 40 and the exterior surface ofdetector 76 with the corrugations running lengthwise of the tube.

The detector element shown generally at 76 has light sensitiveelectrodes 78 supported in a space enclosed by a transparent glassenvelope 8t and supported in a base or socket 82 through which the leads48 may be connected to the electrodes 78 in any desired manner as byconnecting the leads 48 to prongs 83 on the base or socket which in turnare connected to the electrodes. The pins 85 supporting the detector 76and connected with the electrodes 78 may be imbedded in the base 82 andconnected with the prongs 83 or may be removably inserted in matingreceptacles in the socket 82 electrically connected with prongs 83.Washers S6 and 38 are positioned on opposite sides of a flange 84 formedon the base or socket @2. A spring 94) having one end positioned by thebushing 44 presses on the washer 86 and provides a resilient positioningmeans and support tor the detector element 76. The spring 90 thus urgesthe washer 86, the base 82, the washer 88, the corrugated or extendedsurface heat conductor 74, the triangular member 72 and the quartz glasswindow 66 outwardly against the pins 70 and positions the entireassembly within the tube 40. The bushing 44 is held in the tube 40 byscrews 92- and removal of the screws permits removal of the entireassembly or any port-ion thereof up to and including the quartz window.

Air entering the tube 40 from the flexible member 46 is received inchamber 94 in the tube 40. From chamber 94 the air passes through acentral passage 96 in the base 82 and is directed outwardly to theannular passage formed between the detector element glass envelope 80and the inside of tube 40 and thence outwardly past the circumference ofthe quartz window 66. The corrugated or extended surfiace member 74 actsas a heat sink to absorb heat from the detector element 76. Thecorrugated surface supplies a large wind swept area for removal of thisheat. The air passing over and in direct contact with the glass envelope8t of the detector element 76 also serves to rapidly remove heat fromthe detector element. A washer 98 is supported downstream from thewindow 66 between the pins 7t) and 1% and has an inside diameter oraperture sized so as to direct the air stream issuing from the open endof the tube 40 in a substantially cylindrical or parallel sided annulus.This air stream in the form of a cylindrical annulus has very littleoutward divergence, perhaps 10 degrees, and has suflicient energy todeflect any particles that might otherwise tend to enter the end of thetube 49 and contact the quartz window.

Under certain conditions it is desirable to restrict the scanning angleand under those conditions a collimating tube 102 may be substituted forthe washer 98 and provide an extension beyond the open end of the tube44) and which will serve both as a means for reducing the scanning angleand providing additional protection for the window 66.

In a furnace of the type shown in the Armacost patent and which is usedas an example to illustrate and describe the present invention air underpressure for the burners 104, the igniters 106 and for sealing air maybe supplied from a central source such as fan 108.

As shown schematically in FIG. 8 this air is lead through air heaters110 where it suffers a pressure drop and then through burners 104 whereit suffers a further pressure drop then through the furnace 112 and outthe stack 1141. A bypass 116 is taken from the output of the fan 108before it passes through the air heaters and is led to the igniters 106and to sealing air chambers. When operating under normal load the fan 1%may supply a pressure of 40 inches of water and the air heaters andburners may reduce this pressure by say 16 inches of water. Allowing fora six inch water pressure drop through the bypass 1 16 leaves say a teninch differential across and between igniter air chest 118 and thefurnace 112. As cooling air requirements for the above describeddetector are satisfied with 4 to 5 inches of water pressure and 2 to 4cubic feet per minute flow through the tube 40 and 17 cubic feet perminute flow through the tubular member 14 the entire air supply for thecooling requirements for the detector may be bled out of the air chest118 through line 119 without adversely affecting the operation of theigniter or the sealing air. In fact, because of this small pressure andflow requirements for cooling and because the normal pressure and flowrequirements of the furnace are so large in comparison thereto; the airfor the cooling of the flame detector may be bled from substantially anyconvenient source around the boiler without materially adverselyaffecting that source.

Under low load conditions, where the air flow through the burners orrequired by the burners is small, the pressure drop through the airheaters and the burners may not be suflicient to provide thesubstantially 3 inches of water presure required by the igniter and thesealing air. In the event that the differential pressure between thefurnace and the air chest .118 should drop to 3 inches of water a switch120 actuated by the reduced differential pressure will activate abooster fan 122 to bring the pressure in the air chest 118 up to apressure in excess of 3 inches of Water greater than that in thefurnace. As the cooling air supply for the flame detector is, in theillustrative embodiment, taken from the air chest 113 it will continueto be supplied with sufiicient cooling air even under the low loadconditions of the furnace without any auxiliary equipment beingrequired. In the event of failure of the booster fan 122 and thereduction of the air pressure in the air chest 118 below that at whichthe switch is actuated a differential pressure actuated switch (notshown) similar to switch 120 is utilized to open a valve 124 connectedwith the normal high pressure compressed air lines at the boiler totemporarily supply working air to an aspirator 125 to augment thenecessary cooling air until the fault can be located and remedied. Againbecause of the small flow requirements for this cooling system thenormal compressed air supply for sootblowing and burner tilting, etc.can be tapped and bled without the necessity of supplying a largestorage capacity or additional equipment and still not adversely affectthe normal operation of the compressed air supply.

The flame detector circuit which is utilized in the illustrativeembodiment is that disclosed and claimed in Gilbert application SerialNo. 235,098 filed November 2, 1962 for Flame Detector. The internalcooling i.e. along the wires and around the connections and over theexterior surface of the detector 76 is possible because of this circuitin which a short circuit between the electrical conductors 48 orelectrical leakage will not cause a false signal but will merely reducethe amplitude of the pulse signal, complete shorting reducing the flameoutput signal to zero. Reference may be made to the above-identifiedGilbert application for further details of this circuit.

The rigid support member 16 has a ring stop or inwardly directed flange127 secured adjacent the open end thereof which will act as a stop andpositioning means for the tube 40 carrying the detector. The inner airconducting means contains some compressible element such as the conduit46 which may be compressed by bringing the flange member 54- intocontact with the end of casting 3i and securing it in place. Compressionof this compressible member will force and resiliently urge the tube 40against the ring 127 and hold it in place and block the flow of airbetween said member 16 and said tube 40.

The end of tube 41 between the washer 98 and the open end of the tube,is provided with holes 129 which provide air exit means for the airflowing from inside of tubular member 14 and outside of the conduit 46between member 16 and tube 40 and regulate the pressure drop throughtubular member 14. This air will mix with the substantially cylindricalair stream issuing from the end of tube 40, through the aperture in thewasher 93, and assist in providing a high energy air stream which willinsulate the window 66, and in the absence of the window, the detectorelement 76 from flying particles in the furnace. The ring 127 inaddition to providing a stop for the tube 40 acts as a guide for the airissuing from the open end of the rigid member 16.

As provision must be made for removing the detector assembly includingthe casting 52, the conduit 46, the tube as and their associated memberswhile the furnace is in operation and as the pressure inside the furnaceis, in a pressure furnace system, higher than atmospheric pressureprovision must be made for preventing flames and hot gases from flowingout through the tubular member 14 during and while the tube 40 is beingremoved. During the removal operation air under pressure is continuouslysupplied through the air inlet 62 which includes a flexible member suchas a hose 63 and high pressure air is sup plied through the inlet 38 andthe aspirator 36 having outlets 37 to maintain a pressure at the outerend of tube 24 slightly larger than the pressure in the furnace. In aforced draft or suction type of furnace where the furnace is at apressure less than atmospheric the separate supply through inlet 62 maybe omitted as shown in FIG. 5 and the entire air supply both for theexternal and internal cooling of the tube 40 and the air stream externaland internal to the conduit id may be supplied through the air inlet 3by providing holes 126 connecting the chambers 58 and 32 thus permittingair from the chamber 32 to flow through the orifices 126 and into pipe50 and conduit 46. As the pressure in the furnace is less thanatmospheric the detector assembly may be removed through the tubularmember 14 without danger of the flame coming out through the tube.

It is to be understood that the invention is not limited to .thespecific embodiment herein illustrated and described but may be used inother ways without departure from its spirit and that various changescan be made which would come within the scope of the invention which islimited only by the appended claims.

I claim:

1. A flame detector comprising a tube open at both ends, means directinga stream of air along the exterior of said tube for cooling the tubeexterior, a detector ele ment comprising detector members encased in atransparent sealed enclosure in said tube, a corrugated heattransmitting shield between said enclosure and the inner walls of saidtube, a passageway through said tube including a center portion fortransmitting light to said detector and an annular portion defined bysaid enclosure and said shield and means for connecting said passageway,including said center portion, with a source of cooling gas.

2. A flame detector comprising a tube open at one end, a detectorelement in said tube and forming with said tube an annular passageway insaid tube, a window between said element and said open end and spacedfrom the walls of said tube with the window periphery forming, with thetube, an extension of said passageway, means forming an opening in saidtube adjacent said open end larger than said window and directingcooling gases passing across said window periphery and out said open endas a substantially cylindrical annulus extension of the annulus formedby said passageway and means for connecting said tube with a source ofcooling gas.

3. A flame detector comprising a tube open at one end, means for coolingthe tube exterior, a detector element, comprising detector membersencased in a transparent sealed enclosure, and a base enclosingelectrical leads for said members, and supporting said members in saidenclosure in said tube, and substantially filling said tube crosssection except for an annular passageway in said tube defined by saidenclosure wall and the inner walls of said tube and means including apassageway through said base for connecting said annular passageway witha source of cooling gas, and an extended surface heat conductor open atboth ends in said annular passageway and dividing said annularpassageway into longitudinally extending passageways and contacting bothsaid enclosure and the inner walls of said tube.

4. A flame detector comprising a tube open at one end, a detectorelement in said tube and forming with said tube an annular passageway insaid tube, a window between said element and said open end exposed toair flow through said tube and spaced from the walls of said tube withthe window periphery forming with said tube an extension of saidpassageway, means protecting said window from moving objects includingmeans directing cooling air out the open end of said tube in asubstantially parallel sided annular stream and means for connectingsaid tube with a source of cooling air.

5. A detector as claimed in claim 4 in which said directing meansincludes a tubular extension beyond the end of said tube and window.

6. A flame detector comprising a .tubular casing having an open end anda tube having an open end and enclosing a light sensitive flame detectorelement and having a central passageway for transmitting light to saidelement and removably retained in said tubular casing and substantiallyclosing said open end of said casing, means adjacent the other end ofsaid casing for connecting the inside of said casing with a source ofpressure air and supplying a stream of cooling air inside said casingand out of contact with said element, means for discharging only saidair from said casing adjacent said open end of said casing and means fordirecting cooling air from a supply independent of said stream to theinside of said tube and through said passageway in direct contact withsaid element and out the open end of said tube.

7. A flame detector as claimed in claim 6 in which said directing meansincludes separate means connecting the other end of said .tube with saidsupply independent of said means connecting said casing with saidsource.

8. A flame detector comprising a light sensitive flame detector element,a tube open at one end surrounding said element, means closing the otherend of said tube except for a conduit extending from said other end ofsaid tube, means for connecting said conduit with a. source of airpressure for forcing a first stream of air through said conduit, intosaid .tube and around and in direct contact with said element and outsaid open end for direct air cooling of said element, a tubular casingopen at one end, means for releasably retaining said tube and conduit insaid casing with the open end of said tube terminating adjacent the openend of said casing, means for connecting said casing with a source ofair pressure for forcing a second stream of air through said casingoutside of said tube and conduit and out the open end of said casing forcooling said casing, tube and conduit, said tube and conduit completelyseparating said air streams between said respective connecting means andsaid respective open ends.

9. A flame detector as claimed in claim 8 in which said conduit encloseselectrical conductors leading to said element.

10. In combination with a furnace having a normal combustion air supplymeans including an air chest and means for maintaining the air pressurein said chest above a predetermined minimum, said chest having a standbyseparate compressed air supply, a flame scanner including a detectorelement and means for directing a stream of cooling air along and indirect contact with said element, means connecting said air chestdirectly with said stream directing means, and pressure actuated valvemeans connecting said directing means with said compressed air supplywhen the pressure in said chest falls below said minimum.

11. A flame detector as claimed in claim 8 in which said casing is fixedin an opening in a furnace and said element, said tube, said conduit andsaid means for connecting said conduit with a source of air pressure areremovable as a unit from said tubular fixed casing while air is flowingthrough said conduit and tube.

12. In combination with a furnace having a movable burner secured in afurnace wall, a flame scanner adapted to be mounted on said movableburner cfor movement therewith, comprising a tubular support secured tosaid burn-er and including a flexible conduit, a. tubular memberincluding a flexible conduit telescoped with said support and detectormechanism supported in said member, said tubular member adapted to beinserted through said support while secured .to said burner and meansfor removably securing said member in said support and means for forcingseparate streams of cooling air through said tubular support and saidtubular member.

13. A flame scanner, comprising a tubular support having an open end, atubular member having an open end, telescoped with and spaced from saidsupport and defining an annular air passage therebetween, detectormechanism supported in said member, means urging said tubular memberaxially of said tubular support, an inwardly directed flange memberdefining an air exit opening for said member and positioning said memberaxially of said support and blocking one end of said annular passage,air exit means, for said annular passage, in said tubular memberadjacent the open end thereof connecting the blocked end of said annularpassage with the open end of said member and means for forcing a streamof cooling air through said tubular support and a separate stream ofcooling air through said tubular member said streams being combinedadjacent said air exit means.

14. In combination with a furnace having a normal combustion air supplymeans, a duct connecting said supply with said furnace and including anair heater and a burner in said duct, an air chest connected with saidsupply by a conduit bypassing said air heater and burner, meansmaintaining the air pressure in said chest above a predetermined minimumincluding pressure boosting means connected with said conduit forboosting the pressure in said chest, a flame scanner including adetector element and means for directing a stream of cooling air alongand in direct contact with said element, means connecting said chestdirectly with said stream directing means and pressure actuated meansactivating said boosting means when the pressure in said chest fallsbelow said minimum.

15. A combination as claimed in claim 10 including air conducting meansconnecting said supply means and said chest and in which the means formaintaining the air pressure in said chest includes pressure boostingmeans in said air conducting means between said supply means and saidchest and means responsive to the pressure difference between saidfurnace and said chest for controlling operation of said pressureboosting means.

16. A flame detector as claimed in claim 11 including means formaintaining said second stream with said conduit and tube removed fromsaid casing.

17. A flame detector as claimed in claim 8 in combination with a furnacehaving a normal combustion air supply means including an air chest andmeans for maintaining the air pressure in said chest above apredetermined minimum and providing both said sources of air pressurefor said first and second streams of air.

18. A flame detector as claimed in claim 17 in which said detectorelement comprises energy sensitive members encased in a transparentsealed enclosure in direct contact with said first stream and thecooling requirements of said element are satisfied with said firststream of air between two and four cubic feet per minute and said secondstream approximately seventeen cubic feet per minute.

19. A flame detector for detecting the presence and absence of a flame,comprising a detector element having electrical connections, a tube openat one end and surrounding said element, a conduit connected with theother end of said tube and enclosing wires connected with said element,said wires and elements forming part of a fail-safe electrical circuitinwhich complete shorting of the wires or connections will indicateabsence of a flame by reducing the flame output signal to zero, meansconnecting said conduit with a source of air pressure and forcing astream of air through said conduit in contact with said wires and intosaid tube around and in direct contact with said element and saidelectrical connections for direct air cooling of said element.

References Cited by the Examiner UNITED STATES PATENTS 1,945,652 2/1934Martin.

2,054,382 9/1936 Larsen et al. 158-28 2,462,395 2/1949 Heiman 126-1062,481,040 9/1949 RothWell et a1. 15828 2,493,078 1/1950 Mead.

2,592,847 4/1952 Babicz 15828 FOREIGN PATENTS 717,860 11/1954 GreatBritain.

JAMES W. WESTHAVER, Primary Examiner.

1. A FLAME DETECTOR COMPRISING A TUBE OPEN AT BOTH ENDS, MEANS DIRECTINGA STREAM OF AIR ALONG THE EXTERIOR OF SAID TUBE FOR COOLING THE TUBEEXTERIOR, A DETECTOR ELEMENT COMPRISING DETECTOR MEMBERS ENCASED IN ATRANSPARENT SEALED ENCLOSURE IN SAID TUBE, A CORRUGATED HEATTRANSMITTING SHIELD BETWEEN SAID ENCLOSURE AND THE INNER WALLS OF SAIDTUBE, A PASSAGEWAY THROUGH SAID TUBE INCLUD-